lib/Transforms/Instrumentation/SanitizerCoverage.cpp

   1 //===-- SanitizerCoverage.cpp - coverage instrumentation for sanitizers ---===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // Coverage instrumentation done on LLVM IR level, works with Sanitizers.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "llvm/ADT/ArrayRef.h"
  14 #include "llvm/ADT/SmallVector.h"
  15 #include "llvm/Analysis/EHPersonalities.h"
  16 #include "llvm/Analysis/PostDominators.h"
  17 #include "llvm/IR/CFG.h"
  18 #include "llvm/IR/CallSite.h"
  19 #include "llvm/IR/Constant.h"
  20 #include "llvm/IR/DataLayout.h"
  21 #include "llvm/IR/DebugInfo.h"
  22 #include "llvm/IR/Dominators.h"
  23 #include "llvm/IR/Function.h"
  24 #include "llvm/IR/GlobalVariable.h"
  25 #include "llvm/IR/IRBuilder.h"
  26 #include "llvm/IR/InlineAsm.h"
  27 #include "llvm/IR/IntrinsicInst.h"
  28 #include "llvm/IR/Intrinsics.h"
  29 #include "llvm/IR/LLVMContext.h"
  30 #include "llvm/IR/MDBuilder.h"
  31 #include "llvm/IR/Mangler.h"
  32 #include "llvm/IR/Module.h"
  33 #include "llvm/IR/Type.h"
  34 #include "llvm/Support/CommandLine.h"
  35 #include "llvm/Support/Debug.h"
  36 #include "llvm/Support/raw_ostream.h"
  37 #include "llvm/Transforms/Instrumentation.h"
  38 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
  39 #include "llvm/Transforms/Utils/ModuleUtils.h"
  40
  41 using namespace llvm;
  42
  43 #define DEBUG_TYPE "sancov"
  44
  45 static const char *const SanCovTracePCIndirName =
  46     "__sanitizer_cov_trace_pc_indir";
  47 static const char *const SanCovTracePCName = "__sanitizer_cov_trace_pc";
  48 static const char *const SanCovTraceCmp1 = "__sanitizer_cov_trace_cmp1";
  49 static const char *const SanCovTraceCmp2 = "__sanitizer_cov_trace_cmp2";
  50 static const char *const SanCovTraceCmp4 = "__sanitizer_cov_trace_cmp4";
  51 static const char *const SanCovTraceCmp8 = "__sanitizer_cov_trace_cmp8";
  52 static const char *const SanCovTraceConstCmp1 =
  53     "__sanitizer_cov_trace_const_cmp1";
  54 static const char *const SanCovTraceConstCmp2 =
  55     "__sanitizer_cov_trace_const_cmp2";
  56 static const char *const SanCovTraceConstCmp4 =
  57     "__sanitizer_cov_trace_const_cmp4";
  58 static const char *const SanCovTraceConstCmp8 =
  59     "__sanitizer_cov_trace_const_cmp8";
  60 static const char *const SanCovTraceDiv4 = "__sanitizer_cov_trace_div4";
  61 static const char *const SanCovTraceDiv8 = "__sanitizer_cov_trace_div8";
  62 static const char *const SanCovTraceGep = "__sanitizer_cov_trace_gep";
  63 static const char *const SanCovTraceSwitchName = "__sanitizer_cov_trace_switch";
  64 static const char *const SanCovModuleCtorTracePcGuardName =
  65     "sancov.module_ctor_trace_pc_guard";
  66 static const char *const SanCovModuleCtor8bitCountersName =
  67     "sancov.module_ctor_8bit_counters";
  68 static const uint64_t SanCtorAndDtorPriority = 2;
  69
  70 static const char *const SanCovTracePCGuardName =
  71     "__sanitizer_cov_trace_pc_guard";
  72 static const char *const SanCovTracePCGuardInitName =
  73     "__sanitizer_cov_trace_pc_guard_init";
  74 static const char *const SanCov8bitCountersInitName =
  75     "__sanitizer_cov_8bit_counters_init";
  76 static const char *const SanCovPCsInitName = "__sanitizer_cov_pcs_init";
  77
  78 static const char *const SanCovGuardsSectionName = "sancov_guards";
  79 static const char *const SanCovCountersSectionName = "sancov_cntrs";
  80 static const char *const SanCovPCsSectionName = "sancov_pcs";
  81
  82 static const char *const SanCovLowestStackName = "__sancov_lowest_stack";
  83
  84 static cl::opt<int> ClCoverageLevel(
  85     "sanitizer-coverage-level",
  86     cl::desc("Sanitizer Coverage. 0: none, 1: entry block, 2: all blocks, "
  87              "3: all blocks and critical edges"),
  88     cl::Hidden, cl::init(0));
  89
  90 static cl::opt<bool> ClTracePC("sanitizer-coverage-trace-pc",
  91                                cl::desc("Experimental pc tracing"), cl::Hidden,
  92                                cl::init(false));
  93
  94 static cl::opt<bool> ClTracePCGuard("sanitizer-coverage-trace-pc-guard",
  95                                     cl::desc("pc tracing with a guard"),
  96                                     cl::Hidden, cl::init(false));
  97
  98 // If true, we create a global variable that contains PCs of all instrumented
  99 // BBs, put this global into a named section, and pass this section's bounds
 100 // to __sanitizer_cov_pcs_init.
 101 // This way the coverage instrumentation does not need to acquire the PCs
 102 // at run-time. Works with trace-pc-guard and inline-8bit-counters.
 103 static cl::opt<bool> ClCreatePCTable("sanitizer-coverage-pc-table",
 104                                      cl::desc("create a static PC table"),
 105                                      cl::Hidden, cl::init(false));
 106
 107 static cl::opt<bool>
 108     ClInline8bitCounters("sanitizer-coverage-inline-8bit-counters",
 109                          cl::desc("increments 8-bit counter for every edge"),
 110                          cl::Hidden, cl::init(false));
 111
 112 static cl::opt<bool>
 113     ClCMPTracing("sanitizer-coverage-trace-compares",
 114                  cl::desc("Tracing of CMP and similar instructions"),
 115                  cl::Hidden, cl::init(false));
 116
 117 static cl::opt<bool> ClDIVTracing("sanitizer-coverage-trace-divs",
 118                                   cl::desc("Tracing of DIV instructions"),
 119                                   cl::Hidden, cl::init(false));
 120
 121 static cl::opt<bool> ClGEPTracing("sanitizer-coverage-trace-geps",
 122                                   cl::desc("Tracing of GEP instructions"),
 123                                   cl::Hidden, cl::init(false));
 124
 125 static cl::opt<bool>
 126     ClPruneBlocks("sanitizer-coverage-prune-blocks",
 127                   cl::desc("Reduce the number of instrumented blocks"),
 128                   cl::Hidden, cl::init(true));
 129
 130 static cl::opt<bool> ClStackDepth("sanitizer-coverage-stack-depth",
 131                                   cl::desc("max stack depth tracing"),
 132                                   cl::Hidden, cl::init(false));
 133
 134 namespace {
 135
 136 SanitizerCoverageOptions getOptions(int LegacyCoverageLevel) {
 137   SanitizerCoverageOptions Res;
 138   switch (LegacyCoverageLevel) {
 139   case 0:
 140     Res.CoverageType = SanitizerCoverageOptions::SCK_None;
 141     break;
 142   case 1:
 143     Res.CoverageType = SanitizerCoverageOptions::SCK_Function;
 144     break;
 145   case 2:
 146     Res.CoverageType = SanitizerCoverageOptions::SCK_BB;
 147     break;
 148   case 3:
 149     Res.CoverageType = SanitizerCoverageOptions::SCK_Edge;
 150     break;
 151   case 4:
 152     Res.CoverageType = SanitizerCoverageOptions::SCK_Edge;
 153     Res.IndirectCalls = true;
 154     break;
 155   }
 156   return Res;
 157 }
 158
 159 SanitizerCoverageOptions OverrideFromCL(SanitizerCoverageOptions Options) {
 160   // Sets CoverageType and IndirectCalls.
 161   SanitizerCoverageOptions CLOpts = getOptions(ClCoverageLevel);
 162   Options.CoverageType = std::max(Options.CoverageType, CLOpts.CoverageType);
 163   Options.IndirectCalls |= CLOpts.IndirectCalls;
 164   Options.TraceCmp |= ClCMPTracing;
 165   Options.TraceDiv |= ClDIVTracing;
 166   Options.TraceGep |= ClGEPTracing;
 167   Options.TracePC |= ClTracePC;
 168   Options.TracePCGuard |= ClTracePCGuard;
 169   Options.Inline8bitCounters |= ClInline8bitCounters;
 170   Options.PCTable |= ClCreatePCTable;
 171   Options.NoPrune |= !ClPruneBlocks;
 172   Options.StackDepth |= ClStackDepth;
 173   if (!Options.TracePCGuard && !Options.TracePC &&
 174       !Options.Inline8bitCounters && !Options.StackDepth)
 175     Options.TracePCGuard = true; // TracePCGuard is default.
 176   return Options;
 177 }
 178
 179 class SanitizerCoverageModule : public ModulePass {
 180 public:
 181   SanitizerCoverageModule(
 182       const SanitizerCoverageOptions &Options = SanitizerCoverageOptions())
 183       : ModulePass(ID), Options(OverrideFromCL(Options)) {
 184     initializeSanitizerCoverageModulePass(*PassRegistry::getPassRegistry());
 185   }
 186   bool runOnModule(Module &M) override;
 187   bool runOnFunction(Function &F);
 188   static char ID; // Pass identification, replacement for typeid
 189   StringRef getPassName() const override { return "SanitizerCoverageModule"; }
 190
 191   void getAnalysisUsage(AnalysisUsage &AU) const override {
 192     AU.addRequired<DominatorTreeWrapperPass>();
 193     AU.addRequired<PostDominatorTreeWrapperPass>();
 194   }
 195
 196 private:
 197   void InjectCoverageForIndirectCalls(Function &F,
 198                                       ArrayRef<Instruction *> IndirCalls);
 199   void InjectTraceForCmp(Function &F, ArrayRef<Instruction *> CmpTraceTargets);
 200   void InjectTraceForDiv(Function &F,
 201                          ArrayRef<BinaryOperator *> DivTraceTargets);
 202   void InjectTraceForGep(Function &F,
 203                          ArrayRef<GetElementPtrInst *> GepTraceTargets);
 204   void InjectTraceForSwitch(Function &F,
 205                             ArrayRef<Instruction *> SwitchTraceTargets);
 206   bool InjectCoverage(Function &F, ArrayRef<BasicBlock *> AllBlocks,
 207                       bool IsLeafFunc = true);
 208   GlobalVariable *CreateFunctionLocalArrayInSection(size_t NumElements,
 209                                                     Function &F, Type *Ty,
 210                                                     const char *Section);
 211   GlobalVariable *CreatePCArray(Function &F, ArrayRef<BasicBlock *> AllBlocks);
 212   void CreateFunctionLocalArrays(Function &F, ArrayRef<BasicBlock *> AllBlocks);
 213   void InjectCoverageAtBlock(Function &F, BasicBlock &BB, size_t Idx,
 214                              bool IsLeafFunc = true);
 215   Function *CreateInitCallsForSections(Module &M, const char *CtorName,
 216                                        const char *InitFunctionName, Type *Ty,
 217                                        const char *Section);
 218   std::pair<Value *, Value *> CreateSecStartEnd(Module &M, const char *Section,
 219                                                 Type *Ty);
 220
 221   void SetNoSanitizeMetadata(Instruction *I) {
 222     I->setMetadata(I->getModule()->getMDKindID("nosanitize"),
 223                    MDNode::get(*C, None));
 224   }
 225
 226   std::string getSectionName(const std::string &Section) const;
 227   std::string getSectionStart(const std::string &Section) const;
 228   std::string getSectionEnd(const std::string &Section) const;
 229   FunctionCallee SanCovTracePCIndir;
 230   FunctionCallee SanCovTracePC, SanCovTracePCGuard;
 231   FunctionCallee SanCovTraceCmpFunction[4];
 232   FunctionCallee SanCovTraceConstCmpFunction[4];
 233   FunctionCallee SanCovTraceDivFunction[2];
 234   FunctionCallee SanCovTraceGepFunction;
 235   FunctionCallee SanCovTraceSwitchFunction;
 236   GlobalVariable *SanCovLowestStack;
 237   InlineAsm *EmptyAsm;
 238   Type *IntptrTy, *IntptrPtrTy, *Int64Ty, *Int64PtrTy, *Int32Ty, *Int32PtrTy,
 239       *Int16Ty, *Int8Ty, *Int8PtrTy;
 240   Module *CurModule;
 241   std::string CurModuleUniqueId;
 242   Triple TargetTriple;
 243   LLVMContext *C;
 244   const DataLayout *DL;
 245
 246   GlobalVariable *FunctionGuardArray;  // for trace-pc-guard.
 247   GlobalVariable *Function8bitCounterArray;  // for inline-8bit-counters.
 248   GlobalVariable *FunctionPCsArray;  // for pc-table.
 249   SmallVector<GlobalValue *, 20> GlobalsToAppendToUsed;
 250   SmallVector<GlobalValue *, 20> GlobalsToAppendToCompilerUsed;
 251
 252   SanitizerCoverageOptions Options;
 253 };
 254
 255 } // namespace
 256
 257 std::pair<Value *, Value *>
 258 SanitizerCoverageModule::CreateSecStartEnd(Module &M, const char *Section,
 259                                            Type *Ty) {
 260   GlobalVariable *SecStart =
 261       new GlobalVariable(M, Ty, false, GlobalVariable::ExternalLinkage, nullptr,
 262                          getSectionStart(Section));
 263   SecStart->setVisibility(GlobalValue::HiddenVisibility);
 264   GlobalVariable *SecEnd =
 265       new GlobalVariable(M, Ty, false, GlobalVariable::ExternalLinkage,
 266                          nullptr, getSectionEnd(Section));
 267   SecEnd->setVisibility(GlobalValue::HiddenVisibility);
 268   IRBuilder<> IRB(M.getContext());
 269   Value *SecEndPtr = IRB.CreatePointerCast(SecEnd, Ty);
 270   if (!TargetTriple.isOSBinFormatCOFF())
 271     return std::make_pair(IRB.CreatePointerCast(SecStart, Ty), SecEndPtr);
 272
 273   // Account for the fact that on windows-msvc __start_* symbols actually
 274   // point to a uint64_t before the start of the array.
 275   auto SecStartI8Ptr = IRB.CreatePointerCast(SecStart, Int8PtrTy);
 276   auto GEP = IRB.CreateGEP(Int8Ty, SecStartI8Ptr,
 277                            ConstantInt::get(IntptrTy, sizeof(uint64_t)));
 278   return std::make_pair(IRB.CreatePointerCast(GEP, Ty), SecEndPtr);
 279 }
 280
 281 Function *SanitizerCoverageModule::CreateInitCallsForSections(
 282     Module &M, const char *CtorName, const char *InitFunctionName, Type *Ty,
 283     const char *Section) {
 284   auto SecStartEnd = CreateSecStartEnd(M, Section, Ty);
 285   auto SecStart = SecStartEnd.first;
 286   auto SecEnd = SecStartEnd.second;
 287   Function *CtorFunc;
 288   std::tie(CtorFunc, std::ignore) = createSanitizerCtorAndInitFunctions(
 289       M, CtorName, InitFunctionName, {Ty, Ty}, {SecStart, SecEnd});
 290   assert(CtorFunc->getName() == CtorName);
 291
 292   if (TargetTriple.supportsCOMDAT()) {
 293     // Use comdat to dedup CtorFunc.
 294     CtorFunc->setComdat(M.getOrInsertComdat(CtorName));
 295     appendToGlobalCtors(M, CtorFunc, SanCtorAndDtorPriority, CtorFunc);
 296   } else {
 297     appendToGlobalCtors(M, CtorFunc, SanCtorAndDtorPriority);
 298   }
 299
 300   if (TargetTriple.isOSBinFormatCOFF()) {
 301     // In COFF files, if the contructors are set as COMDAT (they are because
 302     // COFF supports COMDAT) and the linker flag /OPT:REF (strip unreferenced
 303     // functions and data) is used, the constructors get stripped. To prevent
 304     // this, give the constructors weak ODR linkage and ensure the linker knows
 305     // to include the sancov constructor. This way the linker can deduplicate
 306     // the constructors but always leave one copy.
 307     CtorFunc->setLinkage(GlobalValue::WeakODRLinkage);
 308     appendToUsed(M, CtorFunc);
 309   }
 310   return CtorFunc;
 311 }
 312
 313 bool SanitizerCoverageModule::runOnModule(Module &M) {
 314   if (Options.CoverageType == SanitizerCoverageOptions::SCK_None)
 315     return false;
 316   C = &(M.getContext());
 317   DL = &M.getDataLayout();
 318   CurModule = &M;
 319   CurModuleUniqueId = getUniqueModuleId(CurModule);
 320   TargetTriple = Triple(M.getTargetTriple());
 321   FunctionGuardArray = nullptr;
 322   Function8bitCounterArray = nullptr;
 323   FunctionPCsArray = nullptr;
 324   IntptrTy = Type::getIntNTy(*C, DL->getPointerSizeInBits());
 325   IntptrPtrTy = PointerType::getUnqual(IntptrTy);
 326   Type *VoidTy = Type::getVoidTy(*C);
 327   IRBuilder<> IRB(*C);
 328   Int64PtrTy = PointerType::getUnqual(IRB.getInt64Ty());
 329   Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty());
 330   Int8PtrTy = PointerType::getUnqual(IRB.getInt8Ty());
 331   Int64Ty = IRB.getInt64Ty();
 332   Int32Ty = IRB.getInt32Ty();
 333   Int16Ty = IRB.getInt16Ty();
 334   Int8Ty = IRB.getInt8Ty();
 335
 336   SanCovTracePCIndir =
 337       M.getOrInsertFunction(SanCovTracePCIndirName, VoidTy, IntptrTy);
 338   // Make sure smaller parameters are zero-extended to i64 as required by the
 339   // x86_64 ABI.
 340   AttributeList SanCovTraceCmpZeroExtAL;
 341   if (TargetTriple.getArch() == Triple::x86_64) {
 342     SanCovTraceCmpZeroExtAL =
 343         SanCovTraceCmpZeroExtAL.addParamAttribute(*C, 0, Attribute::ZExt);
 344     SanCovTraceCmpZeroExtAL =
 345         SanCovTraceCmpZeroExtAL.addParamAttribute(*C, 1, Attribute::ZExt);
 346   }
 347
 348   SanCovTraceCmpFunction[0] =
 349       M.getOrInsertFunction(SanCovTraceCmp1, SanCovTraceCmpZeroExtAL, VoidTy,
 350                             IRB.getInt8Ty(), IRB.getInt8Ty());
 351   SanCovTraceCmpFunction[1] =
 352       M.getOrInsertFunction(SanCovTraceCmp2, SanCovTraceCmpZeroExtAL, VoidTy,
 353                             IRB.getInt16Ty(), IRB.getInt16Ty());
 354   SanCovTraceCmpFunction[2] =
 355       M.getOrInsertFunction(SanCovTraceCmp4, SanCovTraceCmpZeroExtAL, VoidTy,
 356                             IRB.getInt32Ty(), IRB.getInt32Ty());
 357   SanCovTraceCmpFunction[3] =
 358       M.getOrInsertFunction(SanCovTraceCmp8, VoidTy, Int64Ty, Int64Ty);
 359
 360   SanCovTraceConstCmpFunction[0] = M.getOrInsertFunction(
 361       SanCovTraceConstCmp1, SanCovTraceCmpZeroExtAL, VoidTy, Int8Ty, Int8Ty);
 362   SanCovTraceConstCmpFunction[1] = M.getOrInsertFunction(
 363       SanCovTraceConstCmp2, SanCovTraceCmpZeroExtAL, VoidTy, Int16Ty, Int16Ty);
 364   SanCovTraceConstCmpFunction[2] = M.getOrInsertFunction(
 365       SanCovTraceConstCmp4, SanCovTraceCmpZeroExtAL, VoidTy, Int32Ty, Int32Ty);
 366   SanCovTraceConstCmpFunction[3] =
 367       M.getOrInsertFunction(SanCovTraceConstCmp8, VoidTy, Int64Ty, Int64Ty);
 368
 369   {
 370     AttributeList AL;
 371     if (TargetTriple.getArch() == Triple::x86_64)
 372       AL = AL.addParamAttribute(*C, 0, Attribute::ZExt);
 373     SanCovTraceDivFunction[0] =
 374         M.getOrInsertFunction(SanCovTraceDiv4, AL, VoidTy, IRB.getInt32Ty());
 375   }
 376   SanCovTraceDivFunction[1] =
 377       M.getOrInsertFunction(SanCovTraceDiv8, VoidTy, Int64Ty);
 378   SanCovTraceGepFunction =
 379       M.getOrInsertFunction(SanCovTraceGep, VoidTy, IntptrTy);
 380   SanCovTraceSwitchFunction =
 381       M.getOrInsertFunction(SanCovTraceSwitchName, VoidTy, Int64Ty, Int64PtrTy);
 382
 383   Constant *SanCovLowestStackConstant =
 384       M.getOrInsertGlobal(SanCovLowestStackName, IntptrTy);
 385   SanCovLowestStack = dyn_cast<GlobalVariable>(SanCovLowestStackConstant);
 386   if (!SanCovLowestStack) {
 387     C->emitError(StringRef("'") + SanCovLowestStackName +
 388                  "' should not be declared by the user");
 389     return true;
 390   }
 391   SanCovLowestStack->setThreadLocalMode(
 392       GlobalValue::ThreadLocalMode::InitialExecTLSModel);
 393   if (Options.StackDepth && !SanCovLowestStack->isDeclaration())
 394     SanCovLowestStack->setInitializer(Constant::getAllOnesValue(IntptrTy));
 395
 396   // We insert an empty inline asm after cov callbacks to avoid callback merge.
 397   EmptyAsm = InlineAsm::get(FunctionType::get(IRB.getVoidTy(), false),
 398                             StringRef(""), StringRef(""),
 399                             /*hasSideEffects=*/true);
 400
 401   SanCovTracePC = M.getOrInsertFunction(SanCovTracePCName, VoidTy);
 402   SanCovTracePCGuard =
 403       M.getOrInsertFunction(SanCovTracePCGuardName, VoidTy, Int32PtrTy);
 404
 405   for (auto &F : M)
 406     runOnFunction(F);
 407
 408   Function *Ctor = nullptr;
 409
 410   if (FunctionGuardArray)
 411     Ctor = CreateInitCallsForSections(M, SanCovModuleCtorTracePcGuardName,
 412                                       SanCovTracePCGuardInitName, Int32PtrTy,
 413                                       SanCovGuardsSectionName);
 414   if (Function8bitCounterArray)
 415     Ctor = CreateInitCallsForSections(M, SanCovModuleCtor8bitCountersName,
 416                                       SanCov8bitCountersInitName, Int8PtrTy,
 417                                       SanCovCountersSectionName);
 418   if (Ctor && Options.PCTable) {
 419     auto SecStartEnd = CreateSecStartEnd(M, SanCovPCsSectionName, IntptrPtrTy);
 420     FunctionCallee InitFunction = declareSanitizerInitFunction(
 421         M, SanCovPCsInitName, {IntptrPtrTy, IntptrPtrTy});
 422     IRBuilder<> IRBCtor(Ctor->getEntryBlock().getTerminator());
 423     IRBCtor.CreateCall(InitFunction, {SecStartEnd.first, SecStartEnd.second});
 424   }
 425   // We don't reference these arrays directly in any of our runtime functions,
 426   // so we need to prevent them from being dead stripped.
 427   if (TargetTriple.isOSBinFormatMachO())
 428     appendToUsed(M, GlobalsToAppendToUsed);
 429   appendToCompilerUsed(M, GlobalsToAppendToCompilerUsed);
 430   return true;
 431 }
 432
 433 // True if block has successors and it dominates all of them.
 434 static bool isFullDominator(const BasicBlock *BB, const DominatorTree *DT) {
 435   if (succ_begin(BB) == succ_end(BB))
 436     return false;
 437
 438   for (const BasicBlock *SUCC : make_range(succ_begin(BB), succ_end(BB))) {
 439     if (!DT->dominates(BB, SUCC))
 440       return false;
 441   }
 442
 443   return true;
 444 }
 445
 446 // True if block has predecessors and it postdominates all of them.
 447 static bool isFullPostDominator(const BasicBlock *BB,
 448                                 const PostDominatorTree *PDT) {
 449   if (pred_begin(BB) == pred_end(BB))
 450     return false;
 451
 452   for (const BasicBlock *PRED : make_range(pred_begin(BB), pred_end(BB))) {
 453     if (!PDT->dominates(BB, PRED))
 454       return false;
 455   }
 456
 457   return true;
 458 }
 459
 460 static bool shouldInstrumentBlock(const Function &F, const BasicBlock *BB,
 461                                   const DominatorTree *DT,
 462                                   const PostDominatorTree *PDT,
 463                                   const SanitizerCoverageOptions &Options) {
 464   // Don't insert coverage for blocks containing nothing but unreachable: we
 465   // will never call __sanitizer_cov() for them, so counting them in
 466   // NumberOfInstrumentedBlocks() might complicate calculation of code coverage
 467   // percentage. Also, unreachable instructions frequently have no debug
 468   // locations.
 469   if (isa<UnreachableInst>(BB->getFirstNonPHIOrDbgOrLifetime()))
 470     return false;
 471
 472   // Don't insert coverage into blocks without a valid insertion point
 473   // (catchswitch blocks).
 474   if (BB->getFirstInsertionPt() == BB->end())
 475     return false;
 476
 477   if (Options.NoPrune || &F.getEntryBlock() == BB)
 478     return true;
 479
 480   if (Options.CoverageType == SanitizerCoverageOptions::SCK_Function &&
 481       &F.getEntryBlock() != BB)
 482     return false;
 483
 484   // Do not instrument full dominators, or full post-dominators with multiple
 485   // predecessors.
 486   return !isFullDominator(BB, DT)
 487     && !(isFullPostDominator(BB, PDT) && !BB->getSinglePredecessor());
 488 }
 489
 490
 491 // Returns true iff From->To is a backedge.
 492 // A twist here is that we treat From->To as a backedge if
 493 //   * To dominates From or
 494 //   * To->UniqueSuccessor dominates From
 495 static bool IsBackEdge(BasicBlock *From, BasicBlock *To,
 496                        const DominatorTree *DT) {
 497   if (DT->dominates(To, From))
 498     return true;
 499   if (auto Next = To->getUniqueSuccessor())
 500     if (DT->dominates(Next, From))
 501       return true;
 502   return false;
 503 }
 504
 505 // Prunes uninteresting Cmp instrumentation:
 506 //   * CMP instructions that feed into loop backedge branch.
 507 //
 508 // Note that Cmp pruning is controlled by the same flag as the
 509 // BB pruning.
 510 static bool IsInterestingCmp(ICmpInst *CMP, const DominatorTree *DT,
 511                              const SanitizerCoverageOptions &Options) {
 512   if (!Options.NoPrune)
 513     if (CMP->hasOneUse())
 514       if (auto BR = dyn_cast<BranchInst>(CMP->user_back()))
 515         for (BasicBlock *B : BR->successors())
 516           if (IsBackEdge(BR->getParent(), B, DT))
 517             return false;
 518   return true;
 519 }
 520
 521 bool SanitizerCoverageModule::runOnFunction(Function &F) {
 522   if (F.empty())
 523     return false;
 524   if (F.getName().find(".module_ctor") != std::string::npos)
 525     return false; // Should not instrument sanitizer init functions.
 526   if (F.getName().startswith("__sanitizer_"))
 527     return false;  // Don't instrument __sanitizer_* callbacks.
 528   // Don't touch available_externally functions, their actual body is elewhere.
 529   if (F.getLinkage() == GlobalValue::AvailableExternallyLinkage)
 530     return false;
 531   // Don't instrument MSVC CRT configuration helpers. They may run before normal
 532   // initialization.
 533   if (F.getName() == "__local_stdio_printf_options" ||
 534       F.getName() == "__local_stdio_scanf_options")
 535     return false;
 536   if (isa<UnreachableInst>(F.getEntryBlock().getTerminator()))
 537     return false;
 538   // Don't instrument functions using SEH for now. Splitting basic blocks like
 539   // we do for coverage breaks WinEHPrepare.
 540   // FIXME: Remove this when SEH no longer uses landingpad pattern matching.
 541   if (F.hasPersonalityFn() &&
 542       isAsynchronousEHPersonality(classifyEHPersonality(F.getPersonalityFn())))
 543     return false;
 544   if (Options.CoverageType >= SanitizerCoverageOptions::SCK_Edge)
 545     SplitAllCriticalEdges(F, CriticalEdgeSplittingOptions().setIgnoreUnreachableDests());
 546   SmallVector<Instruction *, 8> IndirCalls;
 547   SmallVector<BasicBlock *, 16> BlocksToInstrument;
 548   SmallVector<Instruction *, 8> CmpTraceTargets;
 549   SmallVector<Instruction *, 8> SwitchTraceTargets;
 550   SmallVector<BinaryOperator *, 8> DivTraceTargets;
 551   SmallVector<GetElementPtrInst *, 8> GepTraceTargets;
 552
 553   const DominatorTree *DT =
 554       &getAnalysis<DominatorTreeWrapperPass>(F).getDomTree();
 555   const PostDominatorTree *PDT =
 556       &getAnalysis<PostDominatorTreeWrapperPass>(F).getPostDomTree();
 557   bool IsLeafFunc = true;
 558
 559   for (auto &BB : F) {
 560     if (shouldInstrumentBlock(F, &BB, DT, PDT, Options))
 561       BlocksToInstrument.push_back(&BB);
 562     for (auto &Inst : BB) {
 563       if (Options.IndirectCalls) {
 564         CallSite CS(&Inst);
 565         if (CS && !CS.getCalledFunction())
 566           IndirCalls.push_back(&Inst);
 567       }
 568       if (Options.TraceCmp) {
 569         if (ICmpInst *CMP = dyn_cast<ICmpInst>(&Inst))
 570           if (IsInterestingCmp(CMP, DT, Options))
 571             CmpTraceTargets.push_back(&Inst);
 572         if (isa<SwitchInst>(&Inst))
 573           SwitchTraceTargets.push_back(&Inst);
 574       }
 575       if (Options.TraceDiv)
 576         if (BinaryOperator *BO = dyn_cast<BinaryOperator>(&Inst))
 577           if (BO->getOpcode() == Instruction::SDiv ||
 578               BO->getOpcode() == Instruction::UDiv)
 579             DivTraceTargets.push_back(BO);
 580       if (Options.TraceGep)
 581         if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(&Inst))
 582           GepTraceTargets.push_back(GEP);
 583       if (Options.StackDepth)
 584         if (isa<InvokeInst>(Inst) ||
 585             (isa<CallInst>(Inst) && !isa<IntrinsicInst>(Inst)))
 586           IsLeafFunc = false;
 587     }
 588   }
 589
 590   InjectCoverage(F, BlocksToInstrument, IsLeafFunc);
 591   InjectCoverageForIndirectCalls(F, IndirCalls);
 592   InjectTraceForCmp(F, CmpTraceTargets);
 593   InjectTraceForSwitch(F, SwitchTraceTargets);
 594   InjectTraceForDiv(F, DivTraceTargets);
 595   InjectTraceForGep(F, GepTraceTargets);
 596   return true;
 597 }
 598
 599 GlobalVariable *SanitizerCoverageModule::CreateFunctionLocalArrayInSection(
 600     size_t NumElements, Function &F, Type *Ty, const char *Section) {
 601   ArrayType *ArrayTy = ArrayType::get(Ty, NumElements);
 602   auto Array = new GlobalVariable(
 603       *CurModule, ArrayTy, false, GlobalVariable::PrivateLinkage,
 604       Constant::getNullValue(ArrayTy), "__sancov_gen_");
 605
 606   if (TargetTriple.supportsCOMDAT() && !F.isInterposable())
 607     if (auto Comdat =
 608             GetOrCreateFunctionComdat(F, TargetTriple, CurModuleUniqueId))
 609       Array->setComdat(Comdat);
 610   Array->setSection(getSectionName(Section));
 611   Array->setAlignment(Ty->isPointerTy() ? DL->getPointerSize()
 612                                         : Ty->getPrimitiveSizeInBits() / 8);
 613   GlobalsToAppendToUsed.push_back(Array);
 614   GlobalsToAppendToCompilerUsed.push_back(Array);
 615   MDNode *MD = MDNode::get(F.getContext(), ValueAsMetadata::get(&F));
 616   Array->addMetadata(LLVMContext::MD_associated, *MD);
 617
 618   return Array;
 619 }
 620
 621 GlobalVariable *
 622 SanitizerCoverageModule::CreatePCArray(Function &F,
 623                                        ArrayRef<BasicBlock *> AllBlocks) {
 624   size_t N = AllBlocks.size();
 625   assert(N);
 626   SmallVector<Constant *, 32> PCs;
 627   IRBuilder<> IRB(&*F.getEntryBlock().getFirstInsertionPt());
 628   for (size_t i = 0; i < N; i++) {
 629     if (&F.getEntryBlock() == AllBlocks[i]) {
 630       PCs.push_back((Constant *)IRB.CreatePointerCast(&F, IntptrPtrTy));
 631       PCs.push_back((Constant *)IRB.CreateIntToPtr(
 632           ConstantInt::get(IntptrTy, 1), IntptrPtrTy));
 633     } else {
 634       PCs.push_back((Constant *)IRB.CreatePointerCast(
 635           BlockAddress::get(AllBlocks[i]), IntptrPtrTy));
 636       PCs.push_back((Constant *)IRB.CreateIntToPtr(
 637           ConstantInt::get(IntptrTy, 0), IntptrPtrTy));
 638     }
 639   }
 640   auto *PCArray = CreateFunctionLocalArrayInSection(N * 2, F, IntptrPtrTy,
 641                                                     SanCovPCsSectionName);
 642   PCArray->setInitializer(
 643       ConstantArray::get(ArrayType::get(IntptrPtrTy, N * 2), PCs));
 644   PCArray->setConstant(true);
 645
 646   return PCArray;
 647 }
 648
 649 void SanitizerCoverageModule::CreateFunctionLocalArrays(
 650     Function &F, ArrayRef<BasicBlock *> AllBlocks) {
 651   if (Options.TracePCGuard)
 652     FunctionGuardArray = CreateFunctionLocalArrayInSection(
 653         AllBlocks.size(), F, Int32Ty, SanCovGuardsSectionName);
 654
 655   if (Options.Inline8bitCounters)
 656     Function8bitCounterArray = CreateFunctionLocalArrayInSection(
 657         AllBlocks.size(), F, Int8Ty, SanCovCountersSectionName);
 658
 659   if (Options.PCTable)
 660     FunctionPCsArray = CreatePCArray(F, AllBlocks);
 661 }
 662
 663 bool SanitizerCoverageModule::InjectCoverage(Function &F,
 664                                              ArrayRef<BasicBlock *> AllBlocks,
 665                                              bool IsLeafFunc) {
 666   if (AllBlocks.empty()) return false;
 667   CreateFunctionLocalArrays(F, AllBlocks);
 668   for (size_t i = 0, N = AllBlocks.size(); i < N; i++)
 669     InjectCoverageAtBlock(F, *AllBlocks[i], i, IsLeafFunc);
 670   return true;
 671 }
 672
 673 // On every indirect call we call a run-time function
 674 // __sanitizer_cov_indir_call* with two parameters:
 675 //   - callee address,
 676 //   - global cache array that contains CacheSize pointers (zero-initialized).
 677 //     The cache is used to speed up recording the caller-callee pairs.
 678 // The address of the caller is passed implicitly via caller PC.
 679 // CacheSize is encoded in the name of the run-time function.
 680 void SanitizerCoverageModule::InjectCoverageForIndirectCalls(
 681     Function &F, ArrayRef<Instruction *> IndirCalls) {
 682   if (IndirCalls.empty())
 683     return;
 684   assert(Options.TracePC || Options.TracePCGuard || Options.Inline8bitCounters);
 685   for (auto I : IndirCalls) {
 686     IRBuilder<> IRB(I);
 687     CallSite CS(I);
 688     Value *Callee = CS.getCalledValue();
 689     if (isa<InlineAsm>(Callee))
 690       continue;
 691     IRB.CreateCall(SanCovTracePCIndir, IRB.CreatePointerCast(Callee, IntptrTy));
 692   }
 693 }
 694
 695 // For every switch statement we insert a call:
 696 // __sanitizer_cov_trace_switch(CondValue,
 697 //      {NumCases, ValueSizeInBits, Case0Value, Case1Value, Case2Value, ... })
 698
 699 void SanitizerCoverageModule::InjectTraceForSwitch(
 700     Function &, ArrayRef<Instruction *> SwitchTraceTargets) {
 701   for (auto I : SwitchTraceTargets) {
 702     if (SwitchInst *SI = dyn_cast<SwitchInst>(I)) {
 703       IRBuilder<> IRB(I);
 704       SmallVector<Constant *, 16> Initializers;
 705       Value *Cond = SI->getCondition();
 706       if (Cond->getType()->getScalarSizeInBits() >
 707           Int64Ty->getScalarSizeInBits())
 708         continue;
 709       Initializers.push_back(ConstantInt::get(Int64Ty, SI->getNumCases()));
 710       Initializers.push_back(
 711           ConstantInt::get(Int64Ty, Cond->getType()->getScalarSizeInBits()));
 712       if (Cond->getType()->getScalarSizeInBits() <
 713           Int64Ty->getScalarSizeInBits())
 714         Cond = IRB.CreateIntCast(Cond, Int64Ty, false);
 715       for (auto It : SI->cases()) {
 716         Constant *C = It.getCaseValue();
 717         if (C->getType()->getScalarSizeInBits() <
 718             Int64Ty->getScalarSizeInBits())
 719           C = ConstantExpr::getCast(CastInst::ZExt, It.getCaseValue(), Int64Ty);
 720         Initializers.push_back(C);
 721       }
 722       llvm::sort(Initializers.begin() + 2, Initializers.end(),
 723                  [](const Constant *A, const Constant *B) {
 724                    return cast<ConstantInt>(A)->getLimitedValue() <
 725                           cast<ConstantInt>(B)->getLimitedValue();
 726                  });
 727       ArrayType *ArrayOfInt64Ty = ArrayType::get(Int64Ty, Initializers.size());
 728       GlobalVariable *GV = new GlobalVariable(
 729           *CurModule, ArrayOfInt64Ty, false, GlobalVariable::InternalLinkage,
 730           ConstantArray::get(ArrayOfInt64Ty, Initializers),
 731           "__sancov_gen_cov_switch_values");
 732       IRB.CreateCall(SanCovTraceSwitchFunction,
 733                      {Cond, IRB.CreatePointerCast(GV, Int64PtrTy)});
 734     }
 735   }
 736 }
 737
 738 void SanitizerCoverageModule::InjectTraceForDiv(
 739     Function &, ArrayRef<BinaryOperator *> DivTraceTargets) {
 740   for (auto BO : DivTraceTargets) {
 741     IRBuilder<> IRB(BO);
 742     Value *A1 = BO->getOperand(1);
 743     if (isa<ConstantInt>(A1)) continue;
 744     if (!A1->getType()->isIntegerTy())
 745       continue;
 746     uint64_t TypeSize = DL->getTypeStoreSizeInBits(A1->getType());
 747     int CallbackIdx = TypeSize == 32 ? 0 :
 748         TypeSize == 64 ? 1 : -1;
 749     if (CallbackIdx < 0) continue;
 750     auto Ty = Type::getIntNTy(*C, TypeSize);
 751     IRB.CreateCall(SanCovTraceDivFunction[CallbackIdx],
 752                    {IRB.CreateIntCast(A1, Ty, true)});
 753   }
 754 }
 755
 756 void SanitizerCoverageModule::InjectTraceForGep(
 757     Function &, ArrayRef<GetElementPtrInst *> GepTraceTargets) {
 758   for (auto GEP : GepTraceTargets) {
 759     IRBuilder<> IRB(GEP);
 760     for (auto I = GEP->idx_begin(); I != GEP->idx_end(); ++I)
 761       if (!isa<ConstantInt>(*I) && (*I)->getType()->isIntegerTy())
 762         IRB.CreateCall(SanCovTraceGepFunction,
 763                        {IRB.CreateIntCast(*I, IntptrTy, true)});
 764   }
 765 }
 766
 767 void SanitizerCoverageModule::InjectTraceForCmp(
 768     Function &, ArrayRef<Instruction *> CmpTraceTargets) {
 769   for (auto I : CmpTraceTargets) {
 770     if (ICmpInst *ICMP = dyn_cast<ICmpInst>(I)) {
 771       IRBuilder<> IRB(ICMP);
 772       Value *A0 = ICMP->getOperand(0);
 773       Value *A1 = ICMP->getOperand(1);
 774       if (!A0->getType()->isIntegerTy())
 775         continue;
 776       uint64_t TypeSize = DL->getTypeStoreSizeInBits(A0->getType());
 777       int CallbackIdx = TypeSize == 8 ? 0 :
 778                         TypeSize == 16 ? 1 :
 779                         TypeSize == 32 ? 2 :
 780                         TypeSize == 64 ? 3 : -1;
 781       if (CallbackIdx < 0) continue;
 782       // __sanitizer_cov_trace_cmp((type_size << 32) | predicate, A0, A1);
 783       auto CallbackFunc = SanCovTraceCmpFunction[CallbackIdx];
 784       bool FirstIsConst = isa<ConstantInt>(A0);
 785       bool SecondIsConst = isa<ConstantInt>(A1);
 786       // If both are const, then we don't need such a comparison.
 787       if (FirstIsConst && SecondIsConst) continue;
 788       // If only one is const, then make it the first callback argument.
 789       if (FirstIsConst || SecondIsConst) {
 790         CallbackFunc = SanCovTraceConstCmpFunction[CallbackIdx];
 791         if (SecondIsConst)
 792           std::swap(A0, A1);
 793       }
 794
 795       auto Ty = Type::getIntNTy(*C, TypeSize);
 796       IRB.CreateCall(CallbackFunc, {IRB.CreateIntCast(A0, Ty, true),
 797               IRB.CreateIntCast(A1, Ty, true)});
 798     }
 799   }
 800 }
 801
 802 void SanitizerCoverageModule::InjectCoverageAtBlock(Function &F, BasicBlock &BB,
 803                                                     size_t Idx,
 804                                                     bool IsLeafFunc) {
 805   BasicBlock::iterator IP = BB.getFirstInsertionPt();
 806   bool IsEntryBB = &BB == &F.getEntryBlock();
 807   DebugLoc EntryLoc;
 808   if (IsEntryBB) {
 809     if (auto SP = F.getSubprogram())
 810       EntryLoc = DebugLoc::get(SP->getScopeLine(), 0, SP);
 811     // Keep static allocas and llvm.localescape calls in the entry block.  Even
 812     // if we aren't splitting the block, it's nice for allocas to be before
 813     // calls.
 814     IP = PrepareToSplitEntryBlock(BB, IP);
 815   } else {
 816     EntryLoc = IP->getDebugLoc();
 817   }
 818
 819   IRBuilder<> IRB(&*IP);
 820   IRB.SetCurrentDebugLocation(EntryLoc);
 821   if (Options.TracePC) {
 822     IRB.CreateCall(SanCovTracePC); // gets the PC using GET_CALLER_PC.
 823     IRB.CreateCall(EmptyAsm, {}); // Avoids callback merge.
 824   }
 825   if (Options.TracePCGuard) {
 826     auto GuardPtr = IRB.CreateIntToPtr(
 827         IRB.CreateAdd(IRB.CreatePointerCast(FunctionGuardArray, IntptrTy),
 828                       ConstantInt::get(IntptrTy, Idx * 4)),
 829         Int32PtrTy);
 830     IRB.CreateCall(SanCovTracePCGuard, GuardPtr);
 831     IRB.CreateCall(EmptyAsm, {}); // Avoids callback merge.
 832   }
 833   if (Options.Inline8bitCounters) {
 834     auto CounterPtr = IRB.CreateGEP(
 835         Function8bitCounterArray->getValueType(), Function8bitCounterArray,
 836         {ConstantInt::get(IntptrTy, 0), ConstantInt::get(IntptrTy, Idx)});
 837     auto Load = IRB.CreateLoad(Int8Ty, CounterPtr);
 838     auto Inc = IRB.CreateAdd(Load, ConstantInt::get(Int8Ty, 1));
 839     auto Store = IRB.CreateStore(Inc, CounterPtr);
 840     SetNoSanitizeMetadata(Load);
 841     SetNoSanitizeMetadata(Store);
 842   }
 843   if (Options.StackDepth && IsEntryBB && !IsLeafFunc) {
 844     // Check stack depth.  If it's the deepest so far, record it.
 845     Function *GetFrameAddr =
 846         Intrinsic::getDeclaration(F.getParent(), Intrinsic::frameaddress);
 847     auto FrameAddrPtr =
 848         IRB.CreateCall(GetFrameAddr, {Constant::getNullValue(Int32Ty)});
 849     auto FrameAddrInt = IRB.CreatePtrToInt(FrameAddrPtr, IntptrTy);
 850     auto LowestStack = IRB.CreateLoad(IntptrTy, SanCovLowestStack);
 851     auto IsStackLower = IRB.CreateICmpULT(FrameAddrInt, LowestStack);
 852     auto ThenTerm = SplitBlockAndInsertIfThen(IsStackLower, &*IP, false);
 853     IRBuilder<> ThenIRB(ThenTerm);
 854     auto Store = ThenIRB.CreateStore(FrameAddrInt, SanCovLowestStack);
 855     SetNoSanitizeMetadata(LowestStack);
 856     SetNoSanitizeMetadata(Store);
 857   }
 858 }
 859
 860 std::string
 861 SanitizerCoverageModule::getSectionName(const std::string &Section) const {
 862   if (TargetTriple.isOSBinFormatCOFF()) {
 863     if (Section == SanCovCountersSectionName)
 864       return ".SCOV$CM";
 865     if (Section == SanCovPCsSectionName)
 866       return ".SCOVP$M";
 867     return ".SCOV$GM"; // For SanCovGuardsSectionName.
 868   }
 869   if (TargetTriple.isOSBinFormatMachO())
 870     return "__DATA,__" + Section;
 871   return "__" + Section;
 872 }
 873
 874 std::string
 875 SanitizerCoverageModule::getSectionStart(const std::string &Section) const {
 876   if (TargetTriple.isOSBinFormatMachO())
 877     return "\1section$start$__DATA$__" + Section;
 878   return "__start___" + Section;
 879 }
 880
 881 std::string
 882 SanitizerCoverageModule::getSectionEnd(const std::string &Section) const {
 883   if (TargetTriple.isOSBinFormatMachO())
 884     return "\1section$end$__DATA$__" + Section;
 885   return "__stop___" + Section;
 886 }
 887
 888
 889 char SanitizerCoverageModule::ID = 0;
 890 INITIALIZE_PASS_BEGIN(SanitizerCoverageModule, "sancov",
 891                       "SanitizerCoverage: TODO."
 892                       "ModulePass",
 893                       false, false)
 894 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
 895 INITIALIZE_PASS_DEPENDENCY(PostDominatorTreeWrapperPass)
 896 INITIALIZE_PASS_END(SanitizerCoverageModule, "sancov",
 897                     "SanitizerCoverage: TODO."
 898                     "ModulePass",
 899                     false, false)
 900 ModulePass *llvm::createSanitizerCoverageModulePass(
 901     const SanitizerCoverageOptions &Options) {
 902   return new SanitizerCoverageModule(Options);
 903 }